Patent GB-605131-A (GB)
Title: Improvements relating to telephone and like selective systems
IPC: H04Q3/00
Filed: 1945-12-14
Abstract: 605,131. Automatic exchange systems. SIEMENS BROS. & CO., Ltd., and LONG, D. P. Dec. 14, 1945, No. 33966. [Class 40 (iv)] In a high-speed single-motion selector a plurality of wiper sets, each comprising two line wire wipers and a test wiper, is provided, a particular one of which is connected up in response to the number of impulses received, marking of the wanted outlet group taking place over a marking wiper of the switch common to all the sets. In this way the number of outlets that can be had from a selector of a given size is increased. As shown, the selector has 16 wipers and arcs of contacts each accommodating 50 outlets, five wipers being associated with each of the line wires and five with the test wire, while the sixteenth is the marking wiper G. A digit switch is provided, having contact arcs M5, M6 and M7 in the line and test wire circuits, the contacts of which are connected in pairs to corresponding wipers of the selector. Each selector arc contains contacts of either one group of fifty outlets, or of two groups together totalling 50, marking being obtained by cross-connections between the marking arc of wiper G and contacts of wiper M3 or M4, or if all groups contain 50 outlets by earthing the arc of wiper G directly. On seizure, A pulls up to the junction loop and is followed by guard relay B and dialling relay C. Impulses received by A are repeated to DM stepping the digit switch and disconnecting a delayed alarm relay over wiper M3. At the end of the train C falls away and the selector driving mechanism MU is started. When the selector wipers reach an idle outlet in the wanted group, the high-speed test relay T pulls up, cuts the drive, busies the outlet and brings up holding relay H, which switches through the line wires and releases A and B. Earth reverted on the test wire from the succeeding circuit brings down T and holds H. At the end of the conversation, H releases and the digit switch and selector home. If an outlet is to be selectable by a pair of values of a digit, a discriminating signal is sent forward. If the value is odd, then when H comes up, the A relay of the subsequent stage operates round the junction loop in series with a discriminating relay, whereas, if the value is even, the positive junction wire is earthed over wiper M2 and the discriminating relay is shunted to prevent its operation. If an outlet group is congested, the selector is stopped on the last contact by the operation of T to battery over resistance YC, and busy tone and busy flash are reverted over the junction, the appropriate overflow meter being operated over wiper M8. Contacts in the arc of M4 relevant to unused numbers are connected to the normal contact in the arc of wiper G so that if a dead number is called T pulls up immediately and NU tone is reverted over the normal contacts of the line wire arcs. Fig. 2 (not shown) illustrates a selector, for use with a junction seized in response to either of a pair of values of a digit, which gives access to ten groups of 25 outlets each. The contact arc of wiper G is divided into two parts, 25 contacts being commoned and connected to a back contact of a discriminating relay, while the other 25 contacts are connected to a front contact of the same relay. The group to be marked is decided by the operation or non- operation of the discriminating relay, wiper and arc M4 not being required for this purpose. In other respects the operation of the selector is similar to that of the Fig. 1 arrangement. Specification 378,585 is referred to.